Pressure vessel and method of welding a pressure vessel sidewall and end cap together

ABSTRACT

A pressure vessel includes: (a) a cylindrical sidewall having a wall thickness, an inside surface, an outside surface, and the cylindrical sidewall extending between a first end and a second end, wherein one of the first end or the second end includes a sidewall edge that forms part of an outwardly opening weld groove; (b) an end cap constructed to engage the cylindrical sidewall edge, the end cap comprising an end cap edge corresponding to the sidewall edge and that, when combined with the sidewall edge, forms the outwardly opening weld groove; (c) a cylindrically extending backer bar located in support of the outwardly opening weld groove formed by the sidewall edge and the end cap edge; and (d) a weld joint formed in the outwardly opening weld groove and holding the cylindrical sidewall to the end cap. A method for welding a pressure vessel sidewall and end cap together is provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of provisional patent ApplicationSer. No. 62/517,575 filed with the United States Patent and TrademarkOffice on Jun. 9, 2016. The entire disclosure of U.S. Application Ser.No. 62/517,575 is incorporated herein by reference.

FIELD OF THE DISCLOSURE

The present disclosure relates to a pressure vessel and to a method ofwelding a pressure vessel sidewall and end cap together. In particular,the pressure vessel can be a hydraulic cylinder having a piston thereinand being ported for the flow of hydraulic fluid into and out of thehydraulic cylinder.

BACKGROUND

Hydraulic cylinders are typically subject to relatively large internalpressures. In order to handle these large internal pressures, thehydraulic cylinder end cap is welded to the hydraulic cylinder sidewall.Because of the high pressures experienced when using the hydrauliccylinder, it is desirable to avoid fatigue and failure of the weld jointduring the useful life of the hydraulic cylinders. A common failure ofhydraulic cylinders can be referred to as weld failure. Hydraulic fluidleaking from a weld joint is often a result of a weld failure.Accordingly, hydraulic cylinder designs that reduce the incidents ofweld failure are desired.

Several weld designs for hydraulic cylinders are described. For example,see U.S. Pat. No. 6,946,221 to Mickelson et al., U.S. Pat. No. 6,694,615to Mickelson, and U.S. Pat. No. 6,637,315 to Mickelson.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional, assembly view of a prior art hydraulic cylinderillustrating how the end cap is welded onto the sidewall.

FIG. 2 is a sectional, assembly view of a hydraulic cylinder accordingto the principles of the present disclosure.

FIG. 3 is a perspective view of a portion of the hydraulic cylinderassembly according to FIG. 2.

FIG. 4 is a sectional view of a portion of the assembly of FIG. 3.

FIG. 5 is an exploded view of a portion of the assembly of FIG. 4.

SUMMARY

A pressure vessel is provided by the present disclosure. The pressurevessel includes: (a) a cylindrical sidewall having a wall thickness, aninside surface, an outside surface, and the cylindrical sidewallextending between a first end and a second end, wherein one of the firstend or the second end includes a sidewall edge that forms part of anoutwardly opening weld groove; (b) an end cap constructed to engage thecylindrical sidewall edge, the end cap comprising an end cap edgecorresponding to the sidewall edge and that, when combined with thesidewall edge, forms the outwardly opening weld groove; (c) acylindrically extending backer bar located in support of the outwardlyopening weld groove formed by the sidewall edge and the end cap edge;and (d) a weld joint formed in the outwardly opening weld groove andholding the cylindrical sidewall to the end cap.

A method for welding a pressure vessel side wall and end cap together isprovided by the present disclosure. The method includes steps of: (a)welding a sidewall edge of cylindrical sidewall to an end cap edge byintroducing molten metal into an outwardly opening weld groove formed bythe sidewall edge and the end cap edge, wherein: (i) the cylindricalsidewall has a wall thickness, an inside surface, an outside surface,and the cylindrical sidewall extending between a first end and a secondend, wherein one of the first end or the second end includes thesidewall edge that forms part of an outwardly opening weld groove; (ii)the end cap comprises an end cap edge corresponding to the sidewall edgeand that, when combined with the sidewall edge, forms the outwardlyopening weld groove; and (iii) a cylindrically extending backer barlocated in support of the outwardly opening weld groove formed by thesidewall edge and the end cap edge; and (b) forming a weld joint in theoutwardly opening weld groove and holding the cylindrical sidewall tothe end cap.

DETAILED DESCRIPTION

The following description is exemplary in nature and is in no wayintended to limit the invention, its application, or uses.

An exemplary prior art hydraulic cylinder is illustrated in FIG. 1 atreference number 10 and is provided in a sectional view. The hydrauliccylinder 10 includes a cylinder barrel or sidewall 12, and an end cap14. Sliding within the cylinder barrel 12 is a piston 16, and extendingfrom the piston 16 is a piston rod 18. The piston rod 18 passes througha gland 20 which is attached to an end of the cylinder barrel 12opposite the end cap 14. Attached to the piston rod 18 opposite thepiston 16 is a piston rod connector 22. The piston rod connector 22 isavailable for attachment to various items or tools for transmission oflineal force. An end cap connector 24 can be provided extending from theend cap 14, and is similarly available for attachment to a desired toolfor the transmission of lineal force. The piston 16 divides the interior25 of the hydraulic cylinder 10 into a first region 26 and a secondregion 28. Hydraulic fluid flowing into the first region 26 causes thepiston 16 to move toward the gland 20, and hydraulic fluid flowing intothe second region 28 causes the piston 16 to move toward the end cap 14.Similarly, hydraulic fluid leaves the first region 26 as the piston 16moves toward the end cap 14, and hydraulic fluid leaves the secondregion 28 as the piston 16 moves toward the gland 20. A first hydraulicfluid line 30 is available for conveying hydraulic fluid to and from thefirst region 26, and a second hydraulic fluid line 32 is available forconveying hydraulic fluid to and from the second region 28.

The hydraulic cylinder 10 is illustrated with a weld groove 34 shownbetween the cylinder barrel 12 and the end cap 14. When the hydrauliccylinder is assembled and available for operation, the groove 34 isfilled with molten metal to form a weld joint. In the location of theweld groove 34, the cylinder barrel 12 provides a sidewall edge 36, andthe end cap 14 provides an end cap edge 38 along a periphery 40 of theend cap 14 that aligns with the sidewall edge 36 of the cylinder barrel12. The edges 36 and 38 form the weld groove 34, and the weld groove 34can be characterized as outwardly opening. The outwardly opening weldgroove 34 can be characterized as having a pointed bottom 35 and theedges 36 and 38 can be provided slanting away from each other from thebottom 35 to the outside hydraulic cylinder surface 39. The weld groovebottom 35 includes a center 42. The end cap edge 38 along the periphery40 of the end cap 14 is recessed from the interior surface 44 of the endcap 14, and the groove center 42 is shown located in extension over theend cap 14.

During the step of welding, the weld groove 14 is filled with moltenmetal and forms a weld joint. Over time and after repeated cycles by thehydraulic cylinder 10, there is a possibility that a crack may start toform along the inside of the cylinder wall 12 at the location of theendcap 14. Continued propagation of the crack can result in failure ofthe hydraulic cylinder.

Now referring to FIG. 2, a hydraulic cylinder according to the presentdisclosure is shown at reference number 60. Similar to the hydrauliccylinder 10, the hydraulic cylinder 60 includes a cylinder barrel orsidewall 62 and an end cap 64. Sliding within the cylinder barrel 62 isa piston 66, and extending from the piston 66 is a piston rod 68. Thepiston rod 68 passes through a gland 70 which is attached to an end ofthe cylinder barrel 62 opposite the end cap 64. Attached to the pistonrod 68 opposite the piston 66 is a piston rod connector 72. The pistonrod connector 72 is available for attachment to various items or toolsfor transmission of lineal force. An end cap connector 74 can beprovided extending from the end cap 64, and is similarly available forattachment to various items or tools for the transmission of linealforce. The piston 66 divides the interior 75 of the hydraulic cylinder60 into a first region 76 and a second region 78. Hydraulic fluidflowing into the first region 76 cause the piston 66 to move toward thegland 70, and hydraulic fluid flowing into the second region 78 causesthe piston 66 to move toward the end cap 64. Similarly, hydraulic fluidleaves the first region 76 as the piston 66 moves toward the end cap 64,and hydraulic fluid leaves the second region 78 as the piston 66 movestoward the gland 70. A first hydraulic fluid line 80 is available forconveying hydraulic fluid to and from the first region 76, and a secondhydraulic fluid line 82 is available for conveying hydraulic fluid toand from the second region 78. The hydraulic cylinder 60 can be referredto as “ported” because the first hydraulic fluid line 80 connects to thefirst region via port 81 and the second hydraulic fluid line 82 connectsto the second region via port 83.

The hydraulic cylinder 60 is illustrated with a weld groove 84 shownbetween the cylinder barrel 62 and the end cap 64. When the hydrauliccylinder is assembled and available for operation, the weld groove 84 isfilled with molten metal to form a weld joint 85 (shown in FIG. 3). FIG.3 is illustrated with a portion of the weld groove 84 free of metal, anda portion of the weld groove 84 filled with metal and forming a weldjoint 85. While the hydraulic cylinder is shown in the drawings anddescribed, at times, without metal filling the weld groove 84, this donefor illustration. It should be understood that the hydraulic cylinder,when assembled for use, includes the weld groove 84 filled with metal asa result of welding to form the weld joint 85. Exemplary techniques forfilling the weld groove 84 or for welding in general include wire feedwelding and submerged arc welding. Furthermore, once the weld groove 84is filled as a result of welding, the weld joint 85 can be virtuallyindistinguishable from a remainder of the sidewall 62 and the end cap64. Of course, it may be possible for an experienced eye to detect theweld joint 85.

Now referring to FIGS. 3-5, a portion of the hydraulic cylinder 60 isshown illustrating the weld groove 84 and the configuration resulting inthe weld joint 85 after welding. In the location of the weld groove 84,the cylinder barrel 62 provides a sidewall edge 86, and the end cap 64includes an end cap edge 88. The end cap edge 88 is provided along aperiphery 90 of the end cap 64 that aligns with the sidewall edge 86 ofthe cylinder barrel 62. The sidewall edge 86 and the end cap edge 88form the weld groove 84. The weld groove 84 can be provided having a Vshape or having a U shape. In general, the weld groove 84 shown can becharacterized as having a U shape with outwardly opening walls. Ingeneral, a U shape is desirable to provide a wide bottom of the groovethat helps create a greater area or region for filling with moltenmetal. In addition, outwardly slanted walls also provide the groove witha greater surface area for attachment and also a wider outwardly openinggroove. The sidewall edge 86 and the end cap edge 88 can be provided asstraight or chamfered (or beveled). When provided as chamfered, it isdesired for the edges to be recessed. In this context, the term“recessed” means that the portion that is chamfered or beveled ischamfered or beveled in a manner that forms an outwardly opening weldgroove 84 from the bottom to the outside surface. In other words, therecess can be characterized as a recess in the outer surface of thesidewall relative to the inside surface of the sidewall, and can becharacterized as a recess in the outer surface of the end cap relativeto an inner portion of the end cap. As shown in FIG. 4, the weld groove84 is provided as a curved or U-shaped groove that provides a relativelywide bottom of the weld groove 84. A wide bottom for the weld groove 84is desirable because it creates a wider weld groove 84 for receipt ofmolten metal. The bottom of weld groove 84 can be referred to as theweld groove base 92. The weld groove base 92 is relatively thin buthelps contain the molten metal. Accordingly, the edges 86 and 88 areshown extending from an outside surface 94 of the sidewall 62 or theoutside surface 96 of the end cap 64, and extending in a chamfer orbevel toward legs 98 and 99. The legs 98 and 99 form the groove base 92.The center of the weld groove 84 along the groove base 92 can bereferred to as the groove center 100. In the case of the weld groove 84shown in FIG. 5, the groove center 100 is at the location where the legs98 and 99 meet. In alternative designs, the weld center is notnecessarily located where the cylinder barrel 62 and the end cap 64meet.

Beneath the weld groove 84 is a backer bar 110. The backer bar 110becomes part of the weld joint as the weld groove 84 is filled withmolten metal and the groove base 92 and the backer bar 110 melt.Accordingly, the thickness of the groove base 92 should be sufficient sothat it melts during the welding operation and thereby becomes welded tothe backer bar 110. The groove base 92 should not be so thick that itdoes not melt and does not weld to the backer bar 110. The thickness ofthe groove base 92 should be sufficient to form the weld groove 84 andto locate the backer bar 110 in contact with the groove base, forexample, as shown in FIG. 5. In addition, the groove base 92 should besufficiently thin so that it melts along with at least a portion of thebacker bar 110 during the step of welding to form the weld joint 85. Thethickness of the groove base 92 can be selected depending on the powerof the welding process. That is, a more powerful welding process maypermit a thicker groove base 92. Preferably, the groove base 92 has athickness of about 0.060 inch to about 0.090 inch at the location whereit is intended to melt and weld to the backer bar 110. The backer bar110 can be provided as a continuous structure supporting the groove base92, and can be provided with an interference fit with the interiorsurface 112 of the groove base 92. The interference fit can be providedas about 0.002 inch to about 0.003 inch. In addition, the backer bar 110can be received within a backer bar groove 120 along the interior face122 of the end cap 64. Accordingly, the interior face 122 provides abacker bar groove 120 sufficiently deep to receive the backer bar 110.The backer bar groove 120 can include an inside groove surface 124 andan outside groove surface 126. The outside groove surface 126corresponds to the inner surface 112 so that there in an interferencefit with the backer bar 110. The interference fit can be about 0.002inch to about 0.003 inch.

To further help relieve the stresses on the weld joint between the sidewall 62 and the end cap 64, the groove center 100 can be located so thatit is not directly over the end cap 64. By way of comparison, the groovecenter 42 shown in FIG. 1 is provided in alignment with a portion of theend cap 14. In contrast, the groove center 100 shown in FIG. 5 islocated so that it is not in alignment with the end cap 64. That is, thegroove center 100 is located extending beyond the interior face 122 ofthe end cap 64.

The above specification provides a complete description of themanufacture and use of the device and method of the invention. Sincemany embodiments of the invention can be made without departing from thespirit and scope of the invention, the invention resides in the claimshereinafter appended.

What is claimed is:
 1. A pressure vessel comprising: (a) a cylindricalsidewall having a wall thickness, an inside surface, an outside surface,and the cylindrical sidewall extending between a first end and a secondend, wherein one of the first end or the second end includes a sidewalledge that forms part of an outwardly opening weld groove; (b) an end capconstructed to engage the cylindrical sidewall edge, the end capcomprising an end cap edge corresponding to the sidewall edge and that,when combined with the sidewall edge, forms the outwardly opening weldgroove; (c) a cylindrically extending backer bar located in support ofthe outwardly opening weld groove formed by the sidewall edge and theend cap edge, and wherein a portion of the cylindrical sidewall and aportion of the end cap form a weld groove base of the outwardly openingweld groove and engages the cylindrically extending backer bar; and (d)a weld joint formed in the outwardly opening weld groove and holding thecylindrical sidewall to the end cap.
 2. A pressure vessel according toclaim 1 wherein: (a) the groove base has a thickness of about 0.060 inchto about 0.090 inch prior to welding.
 3. A pressure vessel according toclaim 1 wherein: (a) the cylindrically extending backer bar forms partof the weld joint.
 4. A pressure vessel according to claim 1 wherein:(a) the end cap includes an end face forming an interior surface of thepressure vessel and a cylindrical groove provided in the end face of theend cap, and wherein the cylindrical groove is constructed to receivethe cylindrically extending backer bar.
 5. A pressure vessel accordingto claim 1 further comprising: (a) a piston constructed to move alongthe inside surface of the cylindrical sidewall between the end cap andan opposite end cap located at the other of the first end or the secondend.
 6. A pressure vessel according to claim 5 wherein: (a) the secondend cap comprises a gland and is constructed to receive a piston rodtherethrough.
 7. A pressure vessel according to claim 6 wherein: (a) thepiston rod extends from the piston.
 8. A pressure vessel according toclaim 5 wherein: (a) the piston divides an interior of the pressurevessel into a first region and a second region.
 9. A pressure vesselaccording to claim 8 wherein: (a) the first region is ported via a firsthydraulic line for flowing hydraulic fluid into and out of the firstregion.
 10. A pressure vessel according to claim 8 wherein: (a) thesecond region is ported via a second hydraulic line for flowinghydraulic fluid into and out of the second region.
 11. A pressure vesselaccording to claim 1 wherein: (a) a center of the outwardly opening weldgroove is located inwardly of an interior face of the end cap, whereinthe interior face of the end cap forms part of an interior of thepressure vessel.
 12. A method for welding a pressure vessel sidewall andend cap together, the method comprising: (a) welding a sidewall edge ofcylindrical sidewall to an end cap edge by introducing molten metal intoan outwardly opening weld groove formed by the sidewall edge and the endcap edge, wherein: (i) the cylindrical sidewall has a wall thickness, aninside surface, an outside surface, and the cylindrical sidewallextending between a first end and a second end, wherein one of the firstend or the second end includes the sidewall edge that forms part of anoutwardly opening weld groove; (ii) the end cap comprises an end capedge corresponding to the sidewall edge and that, when combined with thesidewall edge, forms the outwardly opening weld groove; (iii) acylindrically extending backer bar located in support of the outwardlyopening weld groove formed by the sidewall edge and the end cap edge;and (iv) a portion of the cylindrical sidewall and a portion of the endcap form a weld groove base of the outwardly opening weld groove andengages the cylindrically extending backer bar; (b) forming a weld jointin the outwardly opening weld groove and holding the cylindricalsidewall to the end cap.
 13. A method for welding a pressure vesselsidewall and end cap together according to claim 12 wherein: (a) thegroove base has a thickness of about 0.060 inch to about 0.090 inch. 14.A method for welding a pressure vessel sidewall and end cap togetheraccording to claim 12 wherein: (a) the cylindrically extending backerbar forms part of the weld joint.
 15. A method for welding a pressurevessel sidewall and end cap together according to claim 12 wherein: (a)the end cap includes an end face forming an interior surface of thepressure vessel and a cylindrical groove provided in the end face of theend cap, and wherein the cylindrical groove is constructed to receivethe cylindrically extending backer bar.
 16. A pressure vesselcomprising: (a) a cylindrical sidewall having a wall thickness, aninside surface, an outside surface, and the cylindrical sidewallextending between a first end and a second end, wherein one of the firstend or the second end includes a sidewall edge that forms part of anoutwardly opening weld groove; (b) an end cap constructed to engage thecylindrical sidewall edge, the end cap comprising an end cap edgecorresponding to the sidewall edge and that, when combined with thesidewall edge, forms the outwardly opening weld groove; (c) acylindrically extending backer bar located in support of the outwardlyopening weld groove formed by the sidewall edge and the end cap edge,(d) the end cap includes an end face forming an interior surface of thepressure vessel and a cylindrical groove provided in the end face of theend cap, and wherein the cylindrical groove is constructed to receivethe cylindrically extending backer bar; and (e) a weld joint formed inthe outwardly opening weld groove and holding the cylindrical sidewallto the end cap.
 17. A pressure vessel according to claim 16 wherein: (a)a portion of the cylindrical sidewall and a portion of the end cap forma weld groove base of the outwardly opening weld groove and engages thecylindrically extending backer bar.
 18. A pressure vessel according toclaim 16 wherein: (a) the cylindrically extending backer bar forms partof the weld joint.
 19. A pressure vessel according to claim 16 furthercomprising: (a) a piston constructed to move along the inside surface ofthe cylindrical sidewall between the end cap and an opposite end caplocated at the other of the first end or the second end.
 20. A pressurevessel according to claim 19 wherein: (a) the second end cap comprises agland and is constructed to receive a piston rod therethrough, thepiston rod extends from the piston, the piston divides an interior ofthe pressure vessel into a first region and a second region, the firstregion is ported via a first hydraulic line for flowing hydraulic fluidinto and out of the first region, and the second region is ported via asecond hydraulic line for flowing hydraulic fluid into and out of thesecond region.
 21. A pressure vessel according to claim 16 wherein: (a)a center of the outwardly opening weld groove is located inwardly of aninterior face of the end cap, wherein the interior face of the end capforms part of an interior of the pressure vessel.
 22. A method forwelding a pressure vessel sidewall and end cap together, the methodcomprising: (a) welding a sidewall edge of cylindrical sidewall to anend cap edge by introducing molten metal into an outwardly opening weldgroove formed by the sidewall edge and the end cap edge, wherein: (i)the cylindrical sidewall has a wall thickness, an inside surface, anoutside surface, and the cylindrical sidewall extending between a firstend and a second end, wherein one of the first end or the second endincludes the sidewall edge that forms part of an outwardly opening weldgroove; (ii) the end cap comprises an end cap edge corresponding to thesidewall edge and that, when combined with the sidewall edge, forms theoutwardly opening weld groove; (iii) a cylindrically extending backerbar located in support of the outwardly opening weld groove formed bythe sidewall edge and the end cap edge; and (iv) the end cap includes anend face forming an interior surface of the pressure vessel and acylindrical groove provided in the end face of the end cap, and whereinthe cylindrical groove is constructed to receive the cylindricallyextending backer bar; and (b) forming a weld joint in the outwardlyopening weld groove and holding the cylindrical sidewall to the end cap.